1. Field of the Invention
The present invention relates to a process for producing a denture base, and more particularly to a process for producing an elastic and removable denture base made of a hydrogel which denture base may be removed as desired, for example, while the user is sleeping in bed.
2. Related Art Statement
It is well known that a denture base is one of the important constitutional elements of a removable denture. Such a denture base serves as a base or support for supporting an artificial tooth or teeth by covering mucosa of alveolar crista and gingival mucosa, thereby to transmit occlusal pressure (functional pressure) to gingival mucosa and to disperse chewing reaction evenly.
Known materials for such a denture base include cobalt-chromium alloys, palladium alloys, platinum added with gold, and acrylic resins. However, since these known materials are hard, they often cause rubefaction, pain or inflammation of mucosa around and below the denture base with foreign body feeling, as well as inflammation or pain of mucosa of allveolar crista, pain of alticulatio of maxillae, inflammation of proglossis, abnormal growth of tunica mucosa oris or caries of the remaining (healthy) teeth. In a case where plural teeth remain, a removable partial denture is set between the remaining healthy teeth to fill the defect, this being referred to as a partial prosthesis system. However, in such a partial denture, it is often desired that the base surface area of the denture base is larger than the occlusion surface area of the artificial teeth so that the major portion of the defect alveolar crista is covered by the base portion of the denture base. However, since a denture base having a shape and dimensions enough to fully cover the lost alveolar crista cannot be inserted through the space formed between the occlusion surface of the remaining teeth, such a denture base is not adapated for easy attachment and removal. Under such circumstances, the base surface area of a removable denture base should be decreased to have the dimensions approximate to those of the occlusion surface area to leave some gaps between the denture base and the remaining teeth, leading to detrimental results that the food remaining in these gaps are putrefied to cause caries of the remaining healthy teeth or gingivitis, in addition to serious detraction of the appearance of the denture base.
A partial denture base having a base portion larger than the occlusion surface area may be produced by using a resilient and elastic material, such as rubber, in lieu of metals, alloys or hard synthetic resins. However, the known rubber materials which have been used for such purpose, including vulcanized natural rubber and synthetic rubbers, not only have unpleasant rubber taste and foreign body feeling but also irritate the oral mucosa (mucosa covering alveolar crista and mucosa of palatum durum) and proglossis to induce inflammation of these tisues. A more serious problem of the rubber base materials is that they are rapidly deteriorated by the attack of oils and fats contained in the foods to loose its mechanical strength or to be decomposed to loose its integrity.